code: def test_estimate(self):
      dag1 = self.est1.estimate()
      self.assertTrue(len(dag1.edges()) > 1)
      self.assertTrue(
          set(dag1.edges()).issubset(
              set(
                  [
                      ("X", "sum"),
                      ("Y", "sum"),
                      ("Z", "sum"),
                      ("sum", "X"),
                      ("sum", "Y"),
                      ("sum", "Z"),
                      ("X", "Y"),
                      ("X", "Z"),
                      ("Y", "Z"),
                      ("Y", "X"),
                      ("Z", "X"),
                      ("Z", "Y"),
                  ]
              )
          )
      )
      dag2 = self.est1.estimate(significance_level=0.001)
      self.assertTrue(len(dag2.edges()) > 1)
      self.assertTrue(
          set(dag2.edges()).issubset(
              set(
                  [
                      ("X", "sum"),
                      ("Y", "sum"),
                      ("Z", "sum"),
                      ("sum", "X"),
                      ("sum", "Y"),
                      ("sum", "Z"),
                      ("X", "Y"),
                      ("X", "Z"),
                      ("Y", "Z"),
                      ("Y", "X"),
                      ("Z", "X"),
                      ("Z", "Y"),
                  ]
              )
          )
      )
  
file_path: pgmpy/pgmpy/tests/test_estimators/test_MmhcEstimator.py
imports: import unittest
  import pandas
  import numpy
  from pgmpy.estimators import MmhcEstimator, K2Score
  from pgmpy.factors.discrete import TabularCPD
label_desc: Use image node_id 2 for calling the TestMmhcEstimator obj's underlying member method code with example usage: obj.test_estimate() without return types